1. Field of Invention
The present invention relates to a hydro-carbon injection supply unit, and more particularly, to a hydro-carbon injection supply unit which, when a high pressure pulsation is generated in a cylinder head due to a fuel reversed during an operation of an injector, prevents the high pressure pulsation from badly influencing a hydro-carbon injection (HCI) part.
2. Description of Related Art
In general, a hydro-carbon injection (HCI) supply unit refers to a unit for injecting a fuel using an injector mounted to a front end of a diesel oxidization catalyst (DOC) to increase a temperature of exhaust gas passing through a diesel particle filter (DPF).
That is, the HCI unit increases a temperature of exhaust gas while a fuel injected to an exhaust manifold is being burned to oxidize particulate matters (PMs) collected by the DPF, thereby reproducing the DPF.
Here, the reproduction of the DPF means that stuck sooty smoke is burned so that the DPF can be prevented from being blocked and converted into a state where the DPF can be reused.
A unit for this purpose is generally referred to as a hydro-carbon injection supply unit.
An example of the hydro-carbon injection supply unit is configured such that a cylinder head and a fuel filter are connected to a fuel feed line and a fuel is supplied through a HCI feed line branched out from the fuel feed line to be injected to an exhaust manifold at a front end of a catalyst.
Accordingly, the HCI supply unit injects a fuel supplied from a fuel filter 3 to an exhaust manifold with an injector depending on a control condition, so that a temperature of the exhaust gas flowing into the exhaust manifold is increased due to a reaction promotion with a catalyst, making it possible to oxidize the PMs collected by the DPF.
As a result, the DPF having the collected PMs is reproduced through oxidization of the PMs, and the state of the DPF can be converted into a state where the DPF can be reused.
However, in the case of the above-discussed hydro-carbon injection supply unit, a layout where an HCI feed line is branched out from a fuel feed line is formed.
In such a layout, a head discharge pressure pulsation is generated inside a cylinder head by a fuel reversed during an operation of an injector, and the head discharge pressure pulsation itself cannot but be transferred to an HCI pressure pulsation.
The head discharge pressure pulsation is unavoidable in some aspects due to an operation of the injector of the fuel supply system, and the HCI pressure pulsation due to the head discharge pressure pulsation is also inevitable in view of propagation along a fuel flow.
However, when pressure propagates at more than 2.8 bar exceeding 2.5 bar which is a design standard for pressure pulsation, the fuel system is badly influenced.
As an example, if a fuel pulsation at more than approximately 2.8 bar exceeding a design standard is excessively generated, the stability of fuel rail pressure is disturbed and fuel injection uniformity cannot but be lowered. As a result, parts of a fuel system cannot but be damaged.
In particular, due to a tendency toward a strictness of a management standard for fuel efficiency/exhaustion and an increase in emphasis on control of fuel amount, a need to properly manage a pulsation pressure of a fuel system cannot help but significantly increase.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.